1. Field of the Invention
The present invention relates to a piezoelectric actuator used for a liquid jetting apparatus or the like which is configured to jet liquid from nozzles, and the liquid jetting apparatus including the piezoelectric actuator.
2. Description of the Related Art
As a piezoelectric actuator used for an ink-jet head, there is conventionally known a piezoelectric actuator including two piezoelectric layers, a common electrode, and a plurality of individual electrodes. The two piezoelectric layers are stacked on each other to continuously extend over a plurality of pressure chambers. The common electrode is positioned between the two piezoelectric layers to extend over therebetween, and the common electrode is kept at a ground potential. The individual electrodes are respectively arranged on the upper surface of the upper piezoelectric layer positioned on the upper side at portions overlapping with the pressure chambers, and a driving signal is input to the individual electrodes. The portions, of the upper piezoelectric layer, sandwiched between the individual electrodes and the common electrode are polarized in a direction parallel to a thickness direction of the piezoelectric layers. When the driving signal is input to the individual electrodes to cause the potential difference between the individual electrodes and the common electrode, an electric field in a direction parallel to the polarization direction occurs in the portions, of the upper piezoelectric layer, sandwiched between the individual electrodes and the common electrode. This electric field causes the portions of the upper piezoelectric layer to contract in a planar direction. As a result, portions, of the two piezoelectric layers, overlapping with the pressure chambers bend to be convex toward the pressure chambers as a whole. At this time, the volume of each of the pressure chambers is reduced to increase a pressure of the ink in each of the pressure chambers, thereby jetting the ink from each of the nozzles connected to one of the pressure chambers.